The reaction mechanism of the Na-K pump of the red blood cell will be investigated. The effects of ions at the inner and outer surface of the pump and of metabolites at the inner surface of the pump on the pump rate will be determined and from the results of such studies conclusions about the pump mechanism will be drawn. First, we will continue to determine the characteristics of pump inhibition by vanadate and we hope to be able to determine the mechanism by which outside Na counteracts vanadate inhibition. We will pursue these studies by determining whether oligomycin, which selects for the E1P conformation of the pump, has any effect on the development of vanadate inhibition. We willl also seek to determine whether Li, which behaves both like K and like Na, will behave like Na in counteracting vanadate inhibition. We will continue to focus our attention on the mechanism by which inside K stimulates pump rate. We will continue to explore the possibility that inside K increases the concentration of ATP and decreases the concentration of ADP perhaps by increasing the activity of one of the glycolytic enzymes. Finally, we will perform experiments to explore the interaction of Mg with the Na pump and to determine how Mg competes with inhibition by oligomycin and promotes inhibition by vanadate.